Flat or low-sloped roofs are often covered with polymeric membranes. Common among the membranes that have the mechanical properties needed to be technologically useful are thermoset membranes prepared with EPDM rubber or thermoplastic membranes prepared with ethylene-propylene reactor copolymers. These membranes typically contain carbon black and/or mineral fillers, which provide advantageous mechanical properties to the membranes. These membranes also include flame retardants, such as magnesium hydroxide, in order to provide the membranes with sufficient flame resistance.
U.S. Pat. No. 4,996,812 discloses a composite roof structure including a layer of adhesive material, such as a foamed, cellular polyurethane adhesive, along with a flexible rubber or thermoplastic membrane including a fleece-like matting layer secured to the underside thereof. The adhesive is typically sprayed onto the roof substrate wherein, prior to solidification of the adhesive, the fleece-lined membrane is pressed into the adhesive so that the matting becomes embedded therein.
To simplify installation and to minimize costs associated with the polymeric membranes, a need exists for a non-fleece membrane sheet that can be directly adhered to the roof substrate.